The present invention relates to a method for manufacturing tubular knitted items, such as hosiery items or the like, which are closed at an axial end, using a single-cylinder circular machine.
It is known that hosiery items are currently manufactured with circular hosiery knitting machines which form the item generally starting from the upper end of the leg, or top, of the hosiery item, and ending the knitting at the toe, which is left open.
The hosiery items must therefore be subjected to a subsequent darning or looping operation, which closes the toe of the hosiery item in order to form the finished product.
Since the toe closure operation significantly affects the production costs of hosiery items, in recent years methods have been proposed, and machines have been studied, which are meant to manufacture hosiery items with a closed toe, i.e., such as to obtain, at the output of the circular machine that forms them, hosiery items in which the toe is already closed.
One of the proposed methods consists in forming the hosiery item by starting from the toe instead of starting from the top. A method of this kind is performed by means of a single-cylinder knitting machine, which is provided with a half-dial, arranged at the upper end of the needle cylinder and facing, in an upward region, one half of said needle cylinder. Said half-dial is provided with hooks which can be actuated so as to engage the loops of knitting that are knitted by the needles of one half of the needle cylinder and said half-dial can be turned over about a diametrical axis of the needle cylinder in order to face the needles of the other half of the needle cylinder.
According to this method, the half-dial initially faces, in an upward region, a first half of the needle cylinder and, in a first step of knitting, during which the needle cylinder is actuated, with an alternating rotary motion about its axis, with at least one forward movement and at least one return movement, the needles of the first half of the needle cylinder, and the hooks of the overlying half-dial being made to pass in front of a feed of the machine at which a thread is dispensed. During this first step, the hooks are extracted radially, with an end portion, from the half-dial so as to form a support for the thread that is dispensed at that feed and needles of the first half of the needle cylinder are actuated in order to take up the thread, and are alternated with inactive needles, swapping the actuated needles with the inactive needles when the motion of the needle cylinder is reversed.
In a second knitting step, the hooks are retracted into the half-dial, retaining the engaged thread. Then, in a third knitting step, heel knitting is performed with the needles of the first half of the needle cylinder by virtue of an actuation of the needle cylinder with an alternating rotary motion about its own axis.
In a fourth step, the half-dial is turned over, about its diametrical axis, so that its hooks that have retained the thread face the needles of the second half of the needle cylinder.
In a fifth step, the hooks are partially extracted from the half-dial and the needles of the second half on the needle cylinder are also actuated. Meanwhile the needle cylinder is actuated with a continuous rotary motion about its own axis in order to form new loops of knitting with the needles of the second half of the needle cylinder, the loops being knitted in with the thread carried by the hooks, which are then retracted into the half-dial in order to release the previously retained and transferred thread. Finally, the machine is actuated in a conventional manner in order to complete the item, which is thus formed with a closed toe directly in the machine.
Through the years, this method has proved to be susceptible of improvements, such as for example the improvement disclosed in U.S. Pat. No. 5,907,960, in which, during the execution of the first step of the above described method, in the forward and/or return motion of the needle cylinder, the first needle of the second half of the needle cylinder also is made to pass in front of the feed (which dispenses the thread to the needles of the first half of the needle cylinder) and is actuated so as to engage the thread, allowing the thread to be engaged by both of the end hooks of the half-dial. By virtue of this improvement, the hosiery item is perfectly closed also at both ends of the initial row of knitting, which constitutes the toe closure row.
Generally, the above described methods are performed by using a half-dial which is provided with a plurality of radial slots, each arranged between two contiguous axial slots of the curved surface of the needle cylinder; a needle slides inside each one of said slots. A hook is arranged inside each radial slot of the half-dial and is constituted by a laminar body which, at its end directed away from the axis of the needle cylinder, is uncinate and open upward during the first step of knitting, i.e., when the hooks face from above the needles of the first half of the needle cylinder. Said uncinate end has a lug which faces the open end of the uncinate body so as to partially close it. Said lug is meant to support the portions of the loops of knitting that are engaged by the hooks when the half-dial is turned over about the diametrical axis in order to make the hooks face the needles of the second half of the needle cylinder.
An auxiliary hook is furthermore arranged inside each radial slot of the half-dial, to the side of each hook; the end of said auxiliary hook that lies opposite with respect to the axis of the needle cylinder is also uncinate but is orientated in the opposite direction with respect to the uncinate end of the adjacent hook.
Furthermore, in the hook and/or the auxiliary hook the uncinate end portions can flex elastically toward each other as a consequence of the movement of the hooks toward the axis of the needle cylinder, partially retracting into the radial slots of the half-dial so that the uncinate end of the auxiliary hook laterally overlaps the uncinate end of the hook, closing it in order to firmly retain the loops of knitting inside the two uncinate ends of the hook and of the auxiliary hook, respectively, during the overturning of the half-dial about the diametrical axis.
In some cases the auxiliary hook, instead of being physically separate from the hook, is constituted by an elastic lamina which is rigidly fixed to a lateral face of said hook and has an uncinate end which lies opposite the uncinate end of the hook.
The mutual approach of the uncinate ends of the hook and of the auxiliary hook is achieved by providing bends in the hook and/or the auxiliary hook; during the retraction of the hook and of the auxiliary hook into the radial slots of the half-dial, said bends interfere with the side walls of said radial slots, elastically deforming the ends of said elements, causing them to move mutually closer and accordingly causing, by elastic reaction, their mutual spacing as soon as they are partially extracted, starting from their uncinate end, from the radial slots of the half-dial.
The above described conventional methods allow to produce tubular items, particularly hosiery items, which are closed at the toe directly on the machine used to manufacture them, and yield good results in terms of quality only if an elastic thread is used to form the first row of knitting, i.e., the row that in practice constitutes the closure of the toe.
Using an elastic thread, however, provides an elasticized closure of the toe of the hosiery item which is not always appreciated with respect to the conventional closure of the toe performed, by looping or darning, with a practically inextensible thread.